The present invention relates to truck tire treads and tires for steer axles.
The use of treads specifically designed for the steer axle of truck tires has been directed to various forms of rib-type tires. This nondriving axle exhibits cornering and turning loads as well as straight line running loads. Some skilled in the art believe the tread ribs should ideally have a sharp edge adjacent circumferential grooves to provide improved handling.
These sharp edges during normal use can exhibit irregular tread wear. High wear erosion is common in the shoulder region of the tread. This problem was addressed in U.S. Pat. No. 4,480,671 issued Nov. 6, 1984, to Giron. He disclosed the use of a laterally located circumferentially continuous rib 4 that under normal driving conditions is in contact with the road, the force or pressure exerted by the rib 4 on the road being less than the force or pressure of the shoulder rib 6. This prior art tire 2 relied on the laterally located rib to protect the sharp edge of the shoulder rib. This slightly recessed laterally located rib 4 as shown in FIG. 2 was claimed to be in contact with the road surfaces when in normal running conditions, the laterally located rib 4 exhibiting less pressure than shoulder rib 6. One such tire 2 is believed to be the Michelin XZA-1+ steer tire.
An alternative design approach was to have a nonrecessed circumferential rib 3 adjacent a narrow circumferentially continuous groove 7 and shoulder rib 5. Such a tire was commercially sold as the Goodyear G259 steer tire and that tire 1 exhibits a static footprint or tread contact patch as shown in FIG. 3.
Although both of the above-mentioned prior art tire are commercially successful providing tires capable of surviving in excess of 100,000 miles on the original tread, a new and potentially superior solution to irregular tread wear problems has been discovered and is described below.